Measurement of longitudinal spin asymmetries for weak boson production in polarized proton-proton collisions at RHIC

Abstract

We report measurements of single- and double- spin asymmetries for $W^{\pm }$ and $Z/{\gamma }^{\ast }$ boson production in longitudinally polarized $p+p$ collisions at $\sqrt{s}=510$ GeV by the STAR experiment at RHIC. The asymmetries for $W^{\pm }$ were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton's polarized quark distributions at the scale of the $W$ mass. The results are compared to theoretical predictions, constrained by recent polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range $0.05<x<0.2$.

7 pages, 5 figures, Submitted to Physical Review Letters; replaced with published version

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